Azure Cloud Service role instances - auto-scaling - Changing event not firing

Question

I got a Cloud Service deployment with 4 worker roles, one of which got auto-scaling enabled. As soon as auto-scaling occurs, all instances of all roles are recycling.

Ideally, I'd like to stop the roles from recycling or at least terminate the work of all other roles in a controlled way.

I found out, that you can react to the RoleEnvironment.Changing event and cancel it to request a graceful shutdown (i.e. make OnStop being called). However, by adding tracing output to the Changing event handler, I noticed that the Changing event was obviously not even fired, so the cancellation was not being registered either.

private void RoleEnvironmentChanging(object sender, RoleEnvironmentChangingEventArgs e)
{
    // This tracing output does not show up in the logs table.
    Trace.TraceInformation("RoleEnvironmentChanging event fired.");
    if ((e.Changes.Any(change => change is RoleEnvironmentConfigurationSettingChange)))
    {
        // This one neither.
        Trace.TraceInformation("One of the changes is a RoleEnvironmentConfigurationSettingChange. Cancelling..");

        e.Cancel = true;
    }
    if ((e.Changes.Any(change => change is RoleEnvironmentTopologyChange)))
    {
        // This one neither.
        Trace.TraceInformation("One of the changes is a RoleEnvironmentTopologyChange. Cancelling.");

        e.Cancel = true;
    }
}

public override bool OnStart()
{
    // Hook up to the changing event to prevent roles from unnecessarily restarting.
    RoleEnvironment.Changing += RoleEnvironmentChanging;

    // Set the maximum number of concurrent connections
    ServicePointManager.DefaultConnectionLimit = 12;

    bool result = base.OnStart();

    return result;
}

Also adding an internal endpoint to each role did not bring the change. Here the configuration from the .csdef:

<WorkerRole name="MyRole" vmsize="Medium">
[...ConfigurationSettings...]
<Endpoints>
  <InternalEndpoint name="Endpoint1" protocol="http" />
</Endpoints>
</WorkerRole>

Also changing the protocol to "any" wasn't successful.

How can I stop my role instances from recycling after a scaling operation?

EDIT:
» Included code snippets
» Fixed typos

Answer 1

Did you try one of the following?

• Check whether the event is being fired in the instances of role which is auto-scaling (to make sure its not a problem with the internal endpoint)
• Do a complete re-deployment (instead of update).
• Add a short Thread.Sleep() after the Tracing output in the event handler (sometimes the role is being shut down before the trace output can be registered)
• Do a change in one of the configs via the management portal (and check whether event is being triggered)
• Check whether the other events (for instance RoleEnvironment.Changed) are being fired